[San-Diego-pm] An old yet persistent problem

Al Tobey tobert at gmail.com
Sun Sep 26 11:35:21 PDT 2010

On Sun, Sep 26, 2010 at 10:42 AM, Joel Fentin <joel at fentin.com> wrote:

> The browser makers could make this easy but they won't.
> I have needed this for years. Here is the current version of the need:
> After some .JPG files swap names, I want the user to reload the page from
> the server. Not from the cache. Elsewise, the pictures appear in the wrong
> places.
> I've been rummaging Stack Overflow and in plenty of other places, looking
> for advice. None of it works for me.
> 1. The most typical advice is along the lines of:
> <meta http-equiv="Cache-Control" content="no-cache, no-store,
> must-revalidate">
> <META HTTP-EQUIV="Pragma" CONTENT="no-cache">
> <META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
> <META HTTP-EQUIV="Pragma-directive" CONTENT="no-cache">
> <META HTTP-EQUIV="Cache-Directive" CONTENT="no-cache">
> No combination of these works for me.
> 2. The one and only thing that works well is to press the F5 button after
> the page loads. I have not seen an example of this in the Perl code.
> 3. Perhaps there is some javascript that would do the job. I would need it
> to do something like: xxx.pl?ID=1234. Not a link nor a button - but
> executed in and at the end of the Perl script.
> If the cure is to work in only one browser, I prefer Firefox.

Have you tried Etags?

http://developer.yahoo.com/performance/rules.html <- great stuff in there in

Maybe you can add a version string to the image URL and get most of what you
want.   I haven't seen it used for images but it's used quite a bit for

<img src="/images/foo.jpg?v=123456789"/>  This can even point at a regular
file and Apache will eat the query.   If you change the version in your
HTML, it'll bypass your browser cache and come back to the server even if
the filename is the same - at least for <script> tags.

That said, Etag headers per-image are probably what you really want.


> --
> Joel Fentin       tel: 760-749-8863
> Biz Website:      http://fentin.com
> Personal Website: http://fentin.com/me
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